MY 88 560SEL idles high at idle. Also, the ABS light is constantly on. I was told that this combination means that the problem lies with the OPV. Where is the OPV & what does it look like? I read on this board that it is behind the battery but I looked back there And I don't think that's where it is on the 560SEL.

Not exactly sure where yours is located as I have a 85, but the OVP is a fuse/relay. Mine is located in the fuse box under the hood. It is easily recognized by a 10 amp fuse that sits on top of it. Check the fuse first as a blown fuse will definately make the ABS light come on.